Mycoplasma bovis (M. bovis) is considered to be one of the more pathogenic species of Mycoplasma and causes significant economic losses worldwide. Mycoplasmas cause severe clinical signs in cattle of all ages. M. bovis is the most frequent Mycoplasma pathogen found to cause pneumonia, mastitis, and arthritis in cattle and its etiological role has also been associated with otitis, keratoconjunctivitis, synovitis, and reproductive disorders in cows and bulls. In general, Mycoplasmas are difficult to treat since they lack a cell wall or membrane, which tends to make them resistant to several classes of commonly used broad-spectrum antibiotic treatments. Mycoplasmas differ from viruses in that Mycoplasmas are larger than most viruses and damage tissue cells by attaching to the surface of cells and destroying them, rather than by entering the cells. Animals infected with M. bovis have depressed immune responses and can exhibit signs of M. bovis infection such as fever, depression, anorexia, labored breathing, nasal and ocular discharge, coughing, sneezing, gasping, grunting, lameness and swollen joints, mastitis, middle ear infections, abortions, recumbence and death. The organism persists in unsanitary, warm, moist environments. Mycoplasmas can survive in milk, and even seem to thrive in the presence of large numbers of leukocytes, which are produced in response to the infection.
There are several references available in the art disclosing M. bovis vaccines. U.S. Pat. No. 6,548,069 discloses a vaccine composition that incorporates a whole cell inactivated bacterin containing at least two killed M. bovis strains. Other references available disclose passaging an M. bovis strain less than 10 times to prepare an inactivated vaccine, but do not describe attenuation of an infectious or pathogenic M. bovis strain through serial passaging or any such attenuated live M. bovis strain as the essence of an avirulent live culture vaccine.
The prior art is deficient in that killed M. bovis is not as effective or efficient in lessening the severity of clinical symptoms associated with a Mycoplasma bovis infection. Even passage at a low level does not produce a Mycoplasma vaccine with high efficacy such that clinical symptoms are greatly reduced. The few low passage, inactivated, M. bovis vaccines that are available do not show a large reduction in the severity of clinical symptoms. Additionally, the U.S. Pat. No. 6,548,069 strongly teaches away from the idea of a high passage, attenuated strain of M. bovis being used in an immunogenic or vaccine composition by teaching:
“Because a Mycoplasma isolate may rapidly alter its antigens in culture, high passage strains of greater than about 50 passages may lose infectivity and elicit a poorer immune response when used in a bacterin of the present invention. Therefore, it is preferable to employ freshly isolated strains or cultured strains that are still virulent; that is, strains that have retained the ability to be infectious in the host animal. While no critical number of generations is known to exist, the present invention preferably starts with a Mycoplasma strain which has been passed no more than about ten, and preferably only about five or less times before mass scale production. By using strains with fewer generations in culture, it is believed that the antigens retain their natural state and thus will elicit a protective immune response against the infectious microorganism.”
Bovine viral diarrhea virus (BVDV) type 1 (BVDV-1) and type 2 (BVDV-2) cause bovine viral diarrhea (BVD) and mucosal disease (MD) in cattle (Baker, 1987; Moennig and Plagemann, 1992; Thiel et al., 1996). The division of BVDV into 2 serotypes is based on significant differences at the level of genomic sequences (summarized in Heinz et al., 2000) which are also obvious from limited cross neutralizing antibody reactions (Ridpath et al. 1994). Inactivation of the RNase activity residing within the Erns results in an attenuated apathogenic BVDV which can be used as a modified live vaccine (WO 99/64604, the content of which is entirely incorporated by reference). The international patent application WO2005/111201 (the content of which is entirely incorporated by reference) provides a further generation of an attenuated BVDV suitable for MLV vaccines, which comprises a multiple modified BVDV having at least one mutation in the coding sequence for glycoprotein Erns and at least another mutation in the coding sequence for Npro, wherein said mutation in the coding sequence for glycoprotein Erns leads to inactivation of RNase activity residing in Erns and/or said mutation in the coding sequence for Npro leads to inactivation of said Npro. Furthermore, various conventional attenuated BVDV viruses are known in the art, which are also suitable candidates for vaccine development.
Parainfluenza-3 virus (PI-3) is an RNA virus classified in the paramyxovirus family. Infections caused by PI-3 are common in cattle. Although PI-3 is capable of causing disease, it is usually associated with mild to subclinical infections. The most important role of PI-3 is to serve as an initiator that can lead to the development of secondary bacterial pneumonia. Clinical signs include pyrexia, cough, serous nasal and lacrimal discharge, increased respiratory rate, and increased breath sounds. The severity of clinical signs worsen with the onset of bacterial pneumonia. Fatalities from uncomplicated PI-3 pneumonia are rare. Lesions include cranioventral lung consolidation, bronchiolitis, and alveolitis with marked congestion and haemorrhage. Inclusion bodies may be identified. Most fatal cases will also have a concurrent bacterial bronchopneumonia.
Bovine Respiratory Syncytial Virus (BRSV) is an RNA virus classified as a pneumovirus in the paramyxovirus family. In addition to cattle, sheep and goats can also be infected by respiratory syncytial viruses. This virus was named for its characteristic cytopathic effect—the formation of syncytial cells. BRSV is distributed worldwide, and the virus is indigenous in the cattle population. BRSV infections associated with respiratory disease occur predominantly in young beef and dairy cattle. Passively derived immunity does not appear to prevent BRSV infections but will reduce the severity of disease. Initial exposures to the virus are associated with severe respiratory disease; subsequent exposures result in mild to subclinical disease. BRSV appears to be an important virus in the bovine respiratory disease complex because of its frequency of occurrence, predilection for the lower respiratory tract, and its ability to predispose the respiratory tract to secondary bacterial infection. In outbreaks, morbidity tends to be high, and case fatality can be 0-20%. Signs include increased rectal temperature 40-42° C., depression, decreased feed intake, increased respiratory rate, cough, and nasal and lacrimal discharge. Generally, respiratory signs predominate. Dyspnea may become pronounced in the later stages of the disease. Subcutaneous emphysema is sometimes reported. Secondary bacterial pneumonia is a frequent occurrence. A biphasic disease pattern has been described but is not consistent. Gross lesions include a diffuse interstitial pneumonia with subpleural and interstitial emphysema along with interstitial edema. These lesions are similar to and must be differentiated from other causes of interstitial pneumonia. Histologic examination reveals syncytial cells in bronchiolar epithelium and lung parenchyma, intracytoplasmic inclusion bodies, proliferation and/or degeneration of bronchiolar epithelium, alveolar epithelialization, edema, and hyaline membrane formation.
Bovine Herpesvirus (BHV-1) is associated with several diseases and symptoms in cattle: Infectious bovine rhinotracheitis (IBR), infectious pustular vulvovaginitis (IPV), balanoposthitis, conjunctivitis, abortion, encephalomyelitis, and mastitis. Only a single serotype of BHV-1 is recognized; however, three subtypes of BHV-1 have been described on the basis of endonuclease cleavage patterns of viral DNA. These types are referred to as BHV-1.1 (respiratory subtype), BHV-1.2 (genital subtype), and BHV-1.3 (encephalitic subtype). Recently, BHV-1.3 has been reclassified as a distinct herpesvirus designated BHV-5. BHV-1 infections are widespread in the cattle population. In feedlot cattle, the respiratory form is most common. The viral infection alone is not life-threatening but predisposes cattle to secondary bacterial pneumonia, which may result in death. In breeding cattle, abortion or genital infections are more common. Genital infections can occur in bulls (infectious pustular balanoposthitis) and cows (IPV) within 1-3 days of mating or close contact with an infected animal. Transmission can occur in the absence of visible lesions and through artificial insemination with semen from subclinically infected bulls. Cattle with latent BHV-1 infections generally show no clinical signs when the virus is reactivated, but they do serve as a source of infection for other susceptible animals and thus perpetuate the disease. The incubation period for the respiratory and genital forms is 2-6 days. In the respiratory form, clinical signs range from mild to severe, depending on the presence of secondary bacterial pneumonia. Clinical signs include pyrexia, anorexia, coughing, excessive salivation, nasal discharge that progresses from serous to mucopurulent, conjunctivitis with lacrimal discharge, inflamed nares (hence the common name “red nose”), and dyspnea if the larynx becomes occluded with purulent material. Pustules may develop on the nasal mucosa and later form diphtheritic plaques. Conjunctivitis with corneal opacity may develop as the only manifestation of BHV-1 infection. In the absence of bacterial pneumonia, recovery generally occurs 4-5 days after the onset of clinical signs. Abortions may occur concurrently with respiratory disease but can also occur up to 100 days after infection. Abortions can occur regardless of the severity of disease in the dam. Abortions generally occur during the second half of pregnancy, but early embryonic death may also occur. The first signs of genital infections in cows are frequent urination, elevation of the tailhead, and a mild vaginal discharge. The vulva is swollen, and small papules, then erosions and ulcers, are present on the mucosal surface. If secondary bacterial infections do not occur, animals recover in 10-14 days. If bacterial infection occurs, there may be inflammation of the uterus and transient infertility, with purulent vaginal discharge for several weeks. In bulls, similar lesions occur on the penis and prepuce. BHV-1 infection can be severe in young calves and cause a generalized disease. Pyrexia, ocular and nasal discharges, respiratory distress, diarrhea, incoordination, and eventually convulsions and death may occur in a short period after generalized viral infection. IBR is rarely fatal in cattle unless complicated by bacterial pneumonia. In uncomplicated IBR infections, most lesions are restricted to the upper respiratory tract and trachea. Petechial to ecchymotic hemorrhages may be found in the mucous membranes of the nasal cavity and the paranasal sinuses. Focal areas of necrosis develop in the nose, pharynx, larynx, and trachea. The lesions may coalesce to form plaques. The sinuses are often filled with a serous or serofibrinous exudate. As the disease progresses, the pharynx becomes covered with a serofibrinous exudate, and blood-tinged fluid may be found in the trachea. The pharyngeal and pulmonary lymph nodes may be acutely swollen and hemorrhagic. The tracheitis may extend into the bronchi and bronchioles; when this occurs, epithelium is sloughed in the airways. The viral lesions are often masked by secondary bacterial infections. In young animals with generalized BHV-1 infection, erosions and ulcers overlaid with debris may be found in the nose, esophagus, and forestomachs. In addition, white foci may be found in the liver, kidney, spleen, and lymph nodes. Aborted fetuses may have pale, focal, necrotic lesions in all tissues, but which are especially visible in the liver.
A number of other Bovine Respiratory Viruses have been identified as being involved in BRD. Bovine herpesvirus-4 has been implicated in several diseases, including BRD. Bovine adenovirus has been associated with a wide spectrum of diseases, with bovine adenovirus type 3 being the serotype most often associated with BRD. Two serotypes of bovine rhinovirus have been recognized to cause respiratory tract infections in cattle. Other viruses reported to be associated with BRD include bovine reovirus, enterovirus, and coronavirus. These viruses have a role similar to the other viruses previously discussed in that, in combination with other stressors, they can serve as initiators of bacterial pneumonia. Bovine coronavirus is also commonly associated with diarrhea in calves. It replicates in the epithelium of the upper respiratory tract and in the enterocytes of the intestine, where it produces similar lesions to rotavirus but also infects the epithelial cells of the large intestine to produce atrophy of the colonic ridges. Vaccines are not available for prevention of these viral respiratory diseases.
Bovine rotavirus is the most common viral cause of diarrhea in calves. Group A and B rotavirus are involved, but group A is the most prevalent and clinically important and contains several serotypes of differing virulence. Rotavirus replicates in the mature absorptive and enzyme-producing enterocytes on the villi of the small intestine, leading to rupture and sloughing of the enterocytes with release of virus to infect adjacent cells. Rotavirus does not infect the immature cells of the crypts. With virulent strains of rotavirus, the loss of enterocytes exceeds the ability of the intestinal crypts to replace them; hence, villous height is reduced, with a consequent decrease in intestinal absorptive surface area and intestinal digestive enzyme activity.
Other viruses, including Breda virus, a calici-like virus, Adenovirus, Astrovirus and Parvovirus, have been demonstrated in the feces of calves with diarrhea and can produce diarrhea in calves experimentally. However, these agents can also be demonstrated in the feces of healthy calves. The importance of these agents in the syndrome of neonatal diarrhea has yet to be determined. Mannheimia haemolytica (formerly Pasteurella haemolytica) biotype A, serotype 1 is the bacterium most frequently isolated from the lungs of cattle with BRD. Although less frequently cultured than M. haemolytica, Pasteurella multocida is also an important cause of bacterial pneumonia. When pulmonary abscessation occurs, generally in association with chronic pneumonia, Actinomyces (Arcanobacterium) pyogenes is frequently isolated. Under normal conditions, M. haemolytica generally remains confined to the upper respiratory tract, in particular the tonsillar crypts, and is difficult to culture from healthy cattle. After stress or viral infection, the replication rate of M. haemolytica in the upper respiratory tract increases rapidly, as does the likelihood of culturing the bacterium. The increased bacterial growth rate and colonization of the lungs may be due to suppression of the host's defense mechanism related to environmental stressors or viral infections. It is during this log phase of growth that virulence factors are elaborated by M. haemolytica, such as an exotoxin that has been referred to as leukotoxin. The interaction between the virulence factors of the bacteria and host defenses results in tissue damage and development of pneumonia. Clinical signs of bacterial pneumonia are often preceded by signs of viral infection of the respiratory tract. With the onset of bacterial pneumonia, the severity of clinical signs increases and are characterized by depression and toxemia. There will be pyrexia (40-41° C.); serous to mucopurulent nasal discharge; moist cough; and a rapid, shallow respiratory rate. Auscultation of the cranioventral lung field reveals increased bronchial sounds, crackles, and wheezes. In severe cases, pleurisy may develop, which is characterized by an irregular breathing pattern and grunting on expiration. The animal will become unthrifty in appearance if the pneumonia becomes chronic, which is usually associated with the formation of pulmonary abscesses. M. haemolytica causes a severe, acute fibrinous pneumonia or fibrinonecrotic pneumonia. The pneumonia has a bronchopneumonic pattern. Grossly, there is extensive reddish black to greyish brown cranioventral regions of consolidation with gelatinous thickening of interlobular septa and fibrinous pleuritis. There are extensive thromboses, foci of lung necrosis, and limited evidence of bronchitis and bronchiolitis. P. multocida is associated with a less fulminating fibrinous to fibrinopurulent bronchopneumonia. In contrast to M. haemolytica, P. multocida is associated with only small amounts of fibrin exudation, some thromboses, limited lung necrosis, and suppurative bronchitis and bronchiolitis.
Haemophilus somnus (recently reclassified as Histophilus somni) is being increasingly recognized as an important pathogen in BRD; these bacteria are normal inhabitants of the nasopharynx of cattle. H. somnus infection of the lungs results in purulent bronchopneumonia that may be followed by septicemia and infection of multiple organs. Occasionally, H. somnus is associated with extensive pleuritis. H. somnus can cause an acute, usually fatal, septicemic disease that can involve the nervous, musculoskeletal, circulatory, and respiratory systems, either singly or together. The reproductive system is often affected but usually without the other systems being clinically involved. The disease may be characterized by fever, severe depression, ataxia, weakness, blindness, coma, and death within several hours to several days. It occurs sporadically in individual beef and dairy cattle and is found nearly worldwide. H. somnus is a gram-negative, nonmotile, nonsporeforming, pleomorphic coccobacillus that requires an enriched medium and a microaerophilic atmosphere for culture. It appears to be identical to Histophilus ovis and Haemophilus agni, etiologic agents of ovine septicemia, mastitis, and epididymitis; however, transmission of H. somnus between sheep and cattle has not been demonstrated. Pathogenic and nonpathogenic strains have been differentiated by intracisternal inoculation of young calves with organisms from various sources. Pathogenic and nonpathogenic strains of H. somnus are carried in the sheath and prepuce of males, the vagina of female cattle, and in the nasal passages of both sexes. The organism may colonize the respiratory tract, presumably after inhalation, and is frequently found in urine. Prevalence of the organism in cattle is probably high because high titers of specific antibodies are found in a large proportion of tested cattle. Several disease syndromes caused by H. somnus have been recognized, including thrombomeningoencephalitis, fibrinopurulent bronchopneumonia, fibrinous pleuritis, and polyarthritis. Myocardial and skeletal muscle necroses occur. Suppurative vaginitis, cervicitis, and endometritis have been documented in cows infected experimentally and naturally after breeding, and the organism is a cause of sporadic abortion. Strains of H. somnus that cause disease adhere to the endothelium of vessels, resulting in contraction, exposure of collagen, platelet adhesion, and thrombosis. TME results when this occurs in the brain and associated membranes, after invasion of the organism into the bloodstream of susceptible cattle. Strains may adhere to endothelium in vessels of the pleura, myocardium, synovium, or a variety of other tissues and produce inflammation in those sites (e.g., infections of the larynx and middle ear have been recorded). The susceptibility of individual animals and variations in the preference of strains of the organism for vessels in different tissues may be important in the development of the form of disease, but the mechanisms involved are incompletely understood. Reproductive problems may not necessarily be preceded by bacteremia, but the pathogenesis is poorly defined. A fever as high as 42° C. is often the first sign of disease; however, this usually falls to normal or subnormal within hours. Other findings are determined by the system(s) involved and may include rapid respiration, stiffness, knuckling at the fetlocks, severe depression, ataxia, paralysis, and opisthotonos, followed by coma and death within several hours. Affected animals may be blind, and retinal hemorrhages with grey foci of retinal necrosis are sometimes seen. Signs such as hypersensitivity, convulsions, excitement, nystagmus, and circling occur inconsistently and may be related to the regions of the CNS affected in the course of disease development. Occasionally, animals are found dead, indicating a rapidly fatal course. A marked change in the total and differential WBC count is common; leukopenia and neutropenia occur in severe, usually acute, fatal disease, while neutrophilia may be present in less severe disease. In TME, the total cell count of the CSF is markedly increased, and neutrophils predominate. During septicemia, the organism can be recovered from blood, synovial fluid, CSF, brain, kidneys, urine, and a variety of other organs. The lesions are characterized by vascular thrombosis and infarction of the surrounding tissue. Randomly distributed red to brown foci of necrosis with hemorrhage on the surface and cut sections of the brain and spinal cord, retina, skeletal muscle, myocardium, kidney, intestine, and spleen are characteristic. A fibrinopurulent meningitis with cloudy CSF may sometimes be seen on the surface of the brain and spinal cord, and a polyserositis, especially of joints and pleura, may occur. An acute fibrinous bronchopneumonia with tissue necrosis may develop after airborne infections.
Except for M. bovis, the exact role of mycoplasmas and ureaplasmas in BRD requires better definition. Mycoplasmas can be recovered from the respiratory tract of nonpneumonic calves, but the frequency of isolation is greater in those with respiratory tract disease. The mycoplasmas commonly recovered from the lungs of pneumonic calves include Mycoplasma dispar, Ureaplasma spp. Experimental infections usually result in unapparent to mild signs of respiratory disease. This does not preclude a synergistic role for mycoplasmas in conjunction with viruses and bacteria in BRD. Lesions described include peribronchial and peribronchiolar lymphoid cuffing and alveolitis. Culture of these organisms requires special media and conditions and may take up to a week for growth of the organisms.
Chlamydiae have been identified in various parts of the world as a cause of enzootic pneumonia in calves. The causative agent is Chlamydia psittaci. Some respiratory isolates from calves have properties of immunotypes 1 and 6 and are similar to strains recovered from intestinal infections and abortions of cattle and sheep. Immunotype 6 has been recovered from pneumonic lungs of calves and pigs. Thus, the GI tract must be considered as an important site in the pathogenesis of chlamydial infections and as a natural reservoir and source of the organisms. Chlamydial pneumonia has affected calves under a whole range of conditions, including dairy farms. A synergism between Chlamydia and P. haemolytica has been demonstrated experimentally. Calves with chlamydial pneumonia are usually febrile, lethargic, and dyspneic, and have a serous and later mucopurulent nasal discharge and a dry hacking cough. Calves of weanling age are affected most frequently, but older cattle may also show signs of infection. The acute pulmonary lesion is a bronchointerstitial pneumonia. The anteroventral parts of the lungs are affected but, in severe cases, entire lobes can be involved. The dry cough is attributed to tracheitis. Microscopic changes in the lungs include suppurative bronchitis and alveolitis progressing to type II pneumocyte hyperplasia and interstitial thickening.
Bovine genital campylobacteriosis is a venereal disease of cattle characterized primarily by early embryonic death, infertility, a protracted calving season, and occasionally, abortion. Distribution is probably worldwide. The cause is the motile, gram-negative, curved or spiral, polar flagellated bacterium Campylobacter fetus venerealis or Campylobacter fetus fetus. For many years, it was thought that C. fetus fetus (formerly C. fetus intestinalis) was generally an intestinal organism, only occasionally caused abortion in cattle, and was not a cause of infertility. However, it has been shown that C. fetus fetus can also be a significant cause of the classic infertility syndrome usually attributed to Campylobacter fetus venerealis. There are several strains of C. fetus fetus, and the only way to determine if a strain is a cause of infertility is to test that possibility in a group of heifers. Campylobacter spp are very labile and are destroyed quickly by heating, drying, and exposure to the atmosphere. Unless cultured quickly after collection from the animal and grown under microaerophilic or anaerobic conditions, campylobacters will not grow. Campylobacter fetus is transmitted venereally and also by contaminated instruments, bedding, or by artificial insemination using contaminated semen. Individual bulls vary in their susceptibility to infection because some become permanent carriers, while others appear to be resistant to infection. Bulls can also transmit the infection mechanically for several hours after copulating with an infected cow. In cows, the duration of the carrier state is also variable; some clear the infection rapidly, while others can carry C. fetus for ≧2 yr. IgA antibodies are shed in cervical mucus in significant amounts in ˜50% of cows for several months after infection and are useful diagnostically. Although most of the genital tract may be free of infection when a cow eventually conceives, the vagina may remain chronically infected, even through pregnancy. Cows are systemically normal, but there is are variable degrees of mucopurulent endometritis that causes early embryonic death, prolonged luteal phases, irregular estrous cycles, repeat breeding and, as a result, protracted calving periods. Observed abortions are not common. In herds not managed intensively, disease may be noticed only when pregnancy examinations reveal low or marginally low pregnancy rates but, more importantly, great variations in gestation lengths, especially when the disease has recently been introduced to the herd. In subsequent years, infertility is usually confined to replacement heifers and a few susceptible cows. Bulls are asymptomatic and produce normal semen.
Leptospirosis is a contagious disease of animals, including man, caused by various immunologically distinct leptospiral serovars, most of which are regarded as subgroups of Leptospira interrogans. Infections may be asymptomatic or cause various signs, including fever, icterus, hemoglobinuria, renal failure, infertility, abortion, and death. After acute infection, leptospires frequently localize in the kidneys or reproductive organs and are shed in the urine, sometimes in large numbers for months or years. Because the organisms survive in surface waters for extended periods, the disease is often waterborne. In the U.S. the disease is primarily due to the serovars Leptospira hardjo, Leptospira interrogans serovar hardjo (hardjo Prajitno), L. borgpetersenii serovar hardjo (hardjo Bovis), Leptospira pomona, and Leptospira grippotyphosa. However, Leptospira canicola and Leptospira icterohaemorrhagiae serovars also have been isolated. Calves may have fever, anorexia, and dyspnea, and in Leptospira pomona infections, icterus, hemoglobinuria, and anemia. Body temperature may rise suddenly to 40.5-41° C. Hemoglobinuria rarely lasts longer than 48-72 hrs. Icterus clears rapidly and is followed by anemia. The RBC's begin to increase in number by 4-5 days and return to normal 7-10 days later. However, Leptospira hardjo infections usually do not cause hemolytic anemia, which makes diagnosis more difficult. Morbidity and mortality are higher in calves than in adult cattle. In older cattle, signs vary greatly and diagnosis is more difficult. Enzootic Leptospira hardjo infections, which usually result in abnormal milk, are more obvious in dairy than in beef cattle. Signs usually are restricted to lowered milk and calf production; a hemolytic crisis does not occur. The milk is thick, yellow, and blood-tinged; it may contain clots, although there is little evidence of mammary inflammation. Milk production returns to normal in 10-14 days, even in the absence of treatment. Abortion and stillbirths, which are common in Leptospira pomona infections and sporadic in Leptospira hardjo infections, generally occur 3-10 weeks after initial infection. The abortions are more common during the third trimester. An abortion storm in a breeding herd is often the first indication that leptospirosis exists, because the mild initial signs often pass unnoticed. In endemically infected herds, abortions occur mostly in younger animals and are sporadic, rather than being manifested as abortion storms. Calves reared by previously infected cows are protected by colostral antibodies for up to 6 months. The calves generally have an antibody titer similar to that of their dams. In the acute form, anemia, icterus, hemoglobinuria, and submucosal hemorrhages are prominent. The kidneys are swollen, with multifocal petechial and ecchymotic hemorrhages that become pale with time. The liver may be swollen, with minute areas of focal necrosis. Petechiae in other organs are seen in fulminating cases; however, in the more prevalent Leptospira hardjo infections, the lesions are primarily restricted to the kidneys.
Brucellosis is caused by bacteria of the genus Brucella and is characterized by abortion, retained placenta, and to a lesser extent, orchitis and infection of the accessory sex glands in males. The disease in cattle, water buffalo, and bison is caused almost exclusively by Brucella abortus; however, Brucella suis or Brucella melitensis is occasionally implicated in some cattle herds. Brucella suis does not appear to be contagious from cow to cow. Brucella abortus Infection spreads rapidly and causes many abortions in unvaccinated herds. Typically, in a herd in which disease is endemic, an infected cow aborts only once after exposure; subsequent gestations and lactations appear normal. After exposure, many cattle become bacteremic for a short period and develop agglutinins and other antibodies; others resist infection, and a small percentage of infected cows recover. A positive serum agglutination test usually precedes abortion or a normal parturition but may be delayed in ˜15% of animals. The incubation period may be variable and is related to the stage of gestation at the time of exposure. Organisms are shed in milk and uterine discharges, and the cow may become temporarily sterile. Bacteria may be found in the uterus during pregnancy, uterine involution, and infrequently, for a prolonged time in the nongravid uterus. Shedding from the vagina largely disappears with reduction of the fluids after parturition. Some infected cows that aborted previously shed brucellae from the uterus at subsequent normal parturitions. Organisms are shed in milk for a variable length of time—in most cattle for life. Natural transmission occurs by ingestion of organisms, which are present in large numbers in aborted fetuses, fetal membranes, and uterine discharges. Cattle may ingest contaminated feed and water, or lick contaminated genitals of other animals. Venereal transmission by infected bulls to susceptible cows appears to be rare. Transmission may occur by artificial insemination when Brucella-contaminated semen is deposited in the uterus but, reportedly, not when deposited in the midcervix. Brucellae may enter the body through mucous membranes, conjunctivae, wounds, or even intact skin. Mechanical vectors (eg, other animals, including man) may spread infection. Brucellae have been recovered from fetuses and from manure that has remained in a cool environment for >2 mo. Exposure to direct sunlight kills the organisms within a few hours. Abortion is the most obvious manifestation. Infections may also cause stillborn or weak calves, retained placentas, and reduced milk yield. Usually, general health is not impaired in uncomplicated abortions. Seminal vesicles, ampullae, testicles, and epididymides may be infected in bulls; therefore, organisms are in the semen. Agglutinins may be demonstrated in seminal plasma from infected bulls. Testicular abscesses may occur. Long-standing infections may result in arthritic joints in some cattle.
Clostridia are relatively large, anaerobic, spore-forming, rod-shaped organisms. The spores are oval, sometimes spherical, and are central, subterminal, or terminal in position. The vegetative forms of clostridia in tissue fluids of infected animals occur singly, in pairs, or rarely in chains. Differentiation of the various pathogenic and related species is based on cultural characteristics, spore shape and position, biochemical reactions, and the antigenic specificity of toxins or surface antigens. The natural habitats of the organisms are the soil and intestinal tract of animals, including man. Pathogenic strains may be acquired by susceptible animals either by wound contamination or by ingestion. Diseases thus produced are a constant threat to successful livestock production in many parts of the world.
Clostridium haemolyticum is a soil-borne organism that may be found naturally in the GI tract of cattle. It can survive for long periods in contaminated soil or in bones from carcasses of animals that had been infected. After ingestion, latent spores ultimately become lodged in the liver. The incubation period is extremely variable, and the onset depends on the presence of a locus of anaerobiosis in the liver. Such a nidus for germination is most often caused by fluke infection, much less often by high nitrate content of the diet, accidental liver puncture, liver biopsy, or any other cause of localized necrosis. When conditions for anaerobiosis are favorable, the spores germinate, and the resulting vegetative cells multiply and produce β toxin (phospholipase C), which causes intravascular hemolysis and its sequelae, including hemolytic anemia and hemoglobinuria. Cattle may be found dead without premonitory signs. Usually, there is a sudden onset of severe depression, fever, abdominal pain, dyspnea, dysentery, and hemoglobinuria. Anemia and jaundice are present in varying degrees. Edema of the brisket may occur. Hgb and RBC levels are quite low. The duration of clinical signs varies from ˜12 hr in pregnant cows to ˜3-4 days in other cattle. The mortality in untreated animals is ˜95%. Some cattle suffer from subclinical attacks of the disease and thereafter act as immune carriers. Dehydration, anemia, and sometimes subcutaneous edema are present. There is bloody fluid in the abdominal and thoracic cavities. The lungs are not grossly affected, and the trachea contains bloody froth with hemorrhages in the mucosa. The small intestine and occasionally the large intestine are hemorrhagic; their contents often contain free or clotted blood. An anemic infarct in the liver is virtually pathognomonic; it is slightly elevated, lighter in color than the surrounding tissue, and outlined by a bluish red zone of congestion. The kidneys are dark, friable, and usually studded with petechiae. The bladder contains purplish red urine. After death, rigor mortis sets in more rapidly than usual.
Clostridium chauvoei occurs naturally in the intestinal tract of animals. It probably can remain viable in the soil for many years, although it does not actively grow there. Contaminated pasture appears to be a source of organisms. Outbreaks of blackleg have occurred in cattle on farms in which recent excavations have occurred, which suggests that disturbance of soil may activate latent spores. The organisms probably are ingested, pass through the wall of the GI tract, and after gaining access to the bloodstream, deposited in muscle and other tissues. In cattle, blackleg infection is endogenous, in contrast to malignant edema. Lesions develop without any history of wounds, although bruising or excessive exercise may precipitate some cases. Commonly, the animals that contract blackleg are of the beef breeds, in excellent health, gaining weight, and usually the best animals of their group. Outbreaks occur in which a few new cases are found each day for several days. Most cases occur in cattle from 6 months to 2 years old, but thrifty calves as young as 6 weeks and cattle as old as 10-12 years may be affected. The disease usually occurs in summer and fall and is uncommon during the winter. In sheep, the disease is not restricted to the young, and most cases follow some form of injury such as shearing cuts, docking, crutching, or castration. Usually, onset is sudden and a few cattle may be found dead without premonitory signs. Acute lameness and marked depression are common. Initially, there is a fever but, by the time clinical signs are obvious, the temperature may be normal or subnormal. Characteristic edematous and crepitant swellings develop in the hip, shoulder, chest, back, neck, or elsewhere. At first, the swelling is small, hot, and painful. As the disease rapidly progresses, the swelling enlarges, there is crepitation on palpation, and the skin becomes cold and insensitive as the blood supply to the area diminishes. General signs include prostration and tremors. Death occurs in 12-48 hrs. In some cattle, the lesions are restricted to the myocardium and the diaphragm, with no reliable ante mortem evidence of the localized lesion.
Clostridium novyi has been suspected but not yet confirmed as a cause of sudden death in cattle and pigs fed high-level grain diets, and in which pre-existing lesions of the liver were not detectable. The lethal and necrotizing toxins (primarily α toxin) damage hepatic parenchyma, thereby permitting the bacteria to multiply and produce a lethal amount of toxin. Usually, death is sudden with no well-defined signs. Affected animals tend to lag behind the flock, assume sternal recumbency, and die within a few hours. Most cases occur in the summer and early fall when liver fluke infection is at its height. The disease is most prevalent in 1- to 4-year-old sheep and is limited to animals infected with liver flukes. Differentiation from acute fascioliasis may be difficult, but peracute deaths of animals that show typical lesions on necropsy should arouse suspicion of infectious necrotic hepatitis. The most characteristic lesions are the greyish yellow necrotic foci in the liver that often follow the migratory tracks of the young flukes. Other common findings are an enlarged pericardial sac filled with straw-colored fluid, and excess fluid in the peritoneal and thoracic cavities. Usually, there is extensive rupture of the capillaries in the subcutaneous tissue, which causes the adjacent skin to turn black (hence the common name, black disease).
Clostridium septicum is found in soil and intestinal contents of animals (including man) throughout the world. Infection ordinarily occurs through contamination of wounds containing devitalized tissue, soil, or some other tissue-debilitant. Wounds caused by accident, castration, docking, unsanitary vaccination, and parturition may become infected. General signs, such as anorexia, intoxication, and high fever, as well as local lesions, develop within a few hours to a few days after predisposing injury. The local lesions are soft swellings that pit on pressure and extend rapidly because of the formation of large quantities of exudate that infiltrates the subcutaneous and intramuscular connective tissue of the affected areas. The muscle in such areas is dark brown to black. Accumulations of gas are uncommon. Severe edema of the head of rams occurs after infection of wounds inflicted by fighting. Malignant edema associated with lacerations of the vulva at parturition is characterized by marked edema of the vulva, severe toxemia, and death in 24-48 hours. Similarity to blackleg is marked, and differentiation made on necropsy is unreliable; laboratory confirmation is the only certain procedure. Horses and pigs are susceptible to malignant edema but not to blackleg.
Infectious disease caused by Clostridium sordellii is also manifested as malignant edema in cattle, and also characterized by a nongaseous, nonhemorrhagic, edematous swelling of the head, face, and neck of young rams. This infection is initiated in young rams by their continual butting of one another. The bruised and battered subcutaneous tissues provide conditions suitable for growth of pathogenic clostridia, and the breaks in the skin offer an opportunity for their entrance
Infection with C. perfringens types A, B and C causes severe enteritis, dysentery, toxemia, and high mortality in young calves. Types B and C both produce the highly necrotizing and lethal β toxin that is responsible for the severe intestinal damage. This toxin is sensitive to proteolytic enzymes, and disease is associated with inhibition of proteolysis in the intestine. Sow colostrum, which contains a trypsin inhibitor, has been suggested as a factor in the susceptibility of young piglets. Type C also causes enterotoxemia in adult cattle. In calves, there is acute diarrhea, dysentery, abdominal pain, convulsions, and opisthotonos. Death may occur in a few hours, but less severe cases survive for a few days, and recovery over a period of several days is possible. Hemorrhagic enteritis with ulceration of the mucosa is the major lesion in all species. Grossly, the affected portion of the intestine is deep blue-purple and appears at first glance to be an infarction associated with mesenteric torsion. Smears of intestinal contents can be examined for large numbers of gram-positive, rod-shaped bacteria, and filtrates made for detection of toxin and subsequent identification by neutralization with specific antiserum.
This classic enterotoxemia caused by C. perfringens type D rarely occurs in cattle. It is worldwide in distribution and may occur in animals of any age. The disease has been suspected in well-nourished beef calves nursing high-producing cows grazing lush pasture and in sudden death syndrome in feedlot cattle; however, supportive laboratory evidence in the latter is lacking. Acutely affected calves not found dead show mania, convulsions, blindness, and death in a few hours. Subacutely affected calves are stuporous for a few days and may recover.
Tetanus toxemia is caused by a specific neurotoxin produced by Clostridium tetani in necrotic tissue. Almost all mammals are susceptible to this disease. Although tetanus is worldwide in distribution, there are some areas, such as the northern Rocky Mountain section of the USA, where the organism is rarely found in the soil and where tetanus is almost unknown. In general, the occurrence of C. tetani in the soil and the incidence of tetanus in man and horses is higher in the warmer parts of the various continents. Clostridium tetani, an anaerobe with terminal, spherical spores, is found in soil and intestinal tracts. In most cases, it is introduced into the tissues through wounds, particularly deep puncture wounds, which provide a suitable anaerobic environment.
Infection with Salmonella spp can produce diarrhea in animals of all ages, especially those that are stressed, closely stocked, or exposed to a heavily contaminated feed or water supply. Salmonellosis is caused by many species of salmonellae and characterized clinically by one or more of three major syndromes—septicemia, acute enteritis, and chronic enteritis. The incidence has increased with the intensification of livestock production. Young calves usually develop the septicemic form. Adult cattle develop acute enteritis. Chronic enteritis may develop occasionally in cattle. Pregnant animals may abort. In older animals, the disease is manifested by dysentery and toxemia, and mortality can be significant. While many other Salmonella spp may cause disease, the more relevant in cattle are S. typhimurium, S. dublin, and S. newport. Although their resulting clinical patterns are not distinct, different species of salmonellae tend to differ in their epidemiology. Plasmid profile and drug-resistance patterns are sometimes useful markers for epidemiologic studies. Feces of infected animals can contaminate feed and water, milk, fresh and processed meats from abattoirs, plant and animal products used as fertilizers or feedstuffs, pasture and rangeland, and many inert materials. The organisms may survive for months in wet, warm areas such as in feeder pig barns or in water dugouts but survive less than 1 week in composted cattle manure. Rodents and wild birds also are sources of infection. The prevalence of infection varies among species and countries and is much higher than the incidence of clinical disease, which is commonly precipitated by stressful situations such as sudden deprivation of feed, transportation, drought, crowding, parturition, and the administration of some drugs.
Further relevant gastro-intestinal pathogens are Escherichia coli, Cryptosporidium parvum and Mycobacterium avium paratuberculosis. Escherichia coli infection causes severe intestinal disease in young animals characterized as neonatal diarrhea, post weaning diarrhea, edema disease, and/or septicemia depending upon the virulence factors present in the strain causing the infection. Calves infected with pathogenic E. coli can develop severe diarrhea causing fatal dehydration, or fatal septicemic infections. Paratuberculosis is a chronic contagious enteritis characterized by persistent and progressive diarrhea, weight loss, debilitation, and eventually death. It affects cattle, sheep, goats, llamas, camels, farmed deer, and other domestic, exotic, and wild ruminants. It has also been recognized in wild rabbits; horses and pigs can be infected experimentally. Distribution is worldwide.
There are conflicting data on the involvement of the organism in Crohn's disease, a chronic enteritis in people. Animals with paratuberculosis should be considered as potential zoonotic risks until the situation is clarified. The causative organism is Mycobacterium avium paratuberculosis, formerly known as M. paratuberculosis or M. johnei. Occasionally, other M. avium subspecies are isolated from cases. The organism is quite resistant and can survive on pasture for more than 1 year, but sunlight, alkaline soils, and drying reduce its survival rate. It is shed in large numbers in feces of infected animals, and infection is acquired by ingestion of contaminated feed and water. Introduction of the disease into a clean herd is usually by subclinically infected carriers. Infection is acquired early in life, but clinical signs rarely develop in cattle <2 years old. Resistance increases with age, and cattle first exposed as adults are unlikely to become infected. Most calves are infected soon after birth either by nursing udders contaminated with feces from infected animals or by being housed in contaminated pens. The organism can also be present in colostrum and milk of infected cows, and intrauterine infections have also been described. After ingestion, the bacteria infect macrophages in the mucosa of the lower small intestine and in associated lymph nodes. Most animals will eliminate infection by an early cell-mediated immune response that encourages microbicidal activity in macrophages. In susceptible animals, the organisms multiply and provoke a chronic enteritis that leads to clinical disease. This may take months to years to develop and is usually paralleled by a decline in cell-mediated immunity and a rise in ineffective serum antibody. However, fecal shedding begins before clinical signs are apparent. Mycobacterium avium paratuberculosis can be isolated from feces, mesenteric and ileocecal lymph nodes, thickened intestinal walls, and less frequently the udder and the reproductive tracts of both sexes.
Cryptosporidiosis is an enterocolitis of cosmopolitan distribution caused by the coccidian parasite Cryptosporidium parvum. It is not host-specific and is common in young ruminants, particularly calves; it is also found in man and pigs and is rare in dogs, cats, and horses. Other cryptosporidia cause disease in reptiles and birds. The disease in calves, characterized by weight loss and watery diarrhea, is clinically indistinguishable from many other causes of calf diarrhea. Cryptosporidium parvum is a minute protozoan that is transmitted by the fecal-oral route. Oocysts are sporulated (four sporozoites) when shed in the feces and, therefore, are immediately infective. The mean incubation period is ˜4 days. Calves 1-3 weeks old seem to be most susceptible. Signs such as anorexia, weight loss, diarrhea, and tenesmus, resemble those caused by several other intestinal pathogens; however, infections without signs do occur. Uncomplicated cryptosporidiosis is seldom fatal. Disease can be severe in immunocompromised individuals. If severe disease in calves is seen, other disease agents or concurrent infections should be ruled out. Although C. parvum can infect virtually the entire intestinal tract, the distal small intestine usually is affected most severely. Infection in horses is limited to the small intestine. Gross lesions may consist of hyperemic intestinal mucosa and yellowish intestinal contents. Microscopically, mild to severe villous atrophy with spherical organisms in the brush border is evident. Unlike Eimeria and Isospora spp, which are intracellular parasites, C. parvum is intramembranous and resides within the brush border of the intestinal epithelial cells.
Inflammation of the mammary gland (mastitis) is almost always due to the effects of infection by bacterial or mycotic pathogens. Mastitis may be associated with infection by many other organisms, including Streptococcus uberis, Streptococcus dysgalactiae, Streptococcus agalactiae, Staphylococcus aureus, Escherichia coli, Klebsiella spp. Pseudomonas aeruginosa, Actinomyces pyogenes, Mycoplasma spp, Nocardia asteroides, Serratia, Mycobacterium spp, Clostridium perfringens, Pasteurella spp, yeasts, and Prototheca spp.
Dermatomycoses (Dermatophytosis) in animals are anthropozoonotic diseases of the skin and related tissue. Clinical symptoms are characterized by loss of hair in the affected area, hyperemia, scaling and asbestos-like scabs. Inflammation is often accompanied by suppuration. Dermatomycoses are often also characterized by localized infection of the skin. Dermatomycoses in animals carry a substantial socioeconomic impact. Diseased animals required prolonged treatment and can spread infection to both animals and humans. Dermatophytosis are caused by mycosis infections of Trichophyton spp. or Microsporum spp. Most relevant causes for cattle are Trichophyton verrucosum, Trichophyton mentagrophytes or Trichophyton sarkisovii. 
An infection of the lower respiratory tract, usually resulting in bronchitis or pneumonia, can be caused by any of several parasitic nematodes, including Dictyocaulus viviparus in cattle. This lungworm belongs to the superfamily Trichostrongyloidea and has direct life cycles. The cattle lungworm is common in northwest Europe and is the cause of severe outbreaks of “husk” or “hoose” in young grazing cattle. Because D. viviparus infection in cattle is the most economically important, it has been most investigated and many of the observations from it are applicable to the other species. Clinical disease usually develops on first exposure to sufficient infective larvae. In cattle, this usually occurs during their first season at pasture; however, an increase in the number of older cattle affected has been reported. Signs of lungworm infection range from moderate coughing with slightly increased respiratory rates to severe persistent coughing and respiratory distress and even failure. Reduced weight-gains, reduced milk yields, and weight loss accompany many infections in cattle. Patent subclinical infections can occur in all species. The most consistent signs in cattle are tachypnea and coughing.
Trichomoniasis is a venereal protozoal disease of cattle characterized primarily by early fetal death and infertility, resulting in extended calving intervals. Distribution is probably worldwide. The causative protozoan, Trichomonas (Tritrichomonas) foetus, is pyriform and ordinarily 10-15×5-10 μm, but there is considerable pleomorphism. It may become spherical when cultured in artificial media. At its anterior end, there are three flagella about the same length as the body of the parasite. An undulating membrane extends the length of the body and is bordered by a marginal filament that continues beyond the membrane as a posterior flagellum. Although T. foetus can survive the process used for freezing semen, it is killed by drying or high temperatures. Trichomonas foetus is found in the genital tracts of cattle. When cows are bred naturally by an infected bull, 30-90% become infected, suggesting that strain differences exist. Variation in breed susceptibility to trichomoniasis may also exist. Bulls of all ages can remain infected indefinitely but this is less likely in younger males. By contrast, most cows are free of infection within 3 months after breeding. However, immunity is not long lasting and reinfection does occur. Transmission can also occur when the semen from infected bulls is used for artificial insemination. The most common sign is infertility caused by embryonic death. This results in repeat breeding and a prolonged calving season. Fetal death and abortions can also occur but are not as common as losses earlier in gestation. Trichomonas foetus has been found in vaginal cultures taken as late as 8 months of gestation and, apparently, live calves can be born to infected dams. Pyometra occasionally develops after breeding.
Neospora caninum is an obligate intracellular protozoan parasite that has been confused previously with Toxoplasma gondii. Only asexual stages are known, and they resemble T. gondii. The complete life cycle of N. caninum is unknown, but it can be transmitted transplacentally in dogs, cattle, goats, sheep, and cats, and subsequent offspring may be affected. Tachyzoites are 5-7×1-5 μm, depending on the stage of division. They divide by endodyogeny. Tachyzoites are found in myocytes, neural cells, dermal cells, macrophages, and other cells. Tissue cysts up to 100 μm in diameter are found in neural cells; the cyst wall is amorphous and up to 4 μm thick. Cysts have no septa and enclose slender 7×1.5 μm bradyzoites. In dairy cattle, N. caninum is a major cause of abortion in many countries, particularly in the USA. Calves may be aborted, stillborn, born underweight, weak, or paralyzed, or they may become paralyzed within 4 weeks of birth. Non-suppurative encephalitis is the main lesion in aborted fetal tissues. Abortion can occur throughout gestation, and some cows may abort again; dams of these calves are clinically normal.
Babesiosis is caused by intraerythrocytic protozoan parasites of the genus Babesia. A wide range of domestic and wild animals and occasionally man is affected by the disease, which is transmitted by ticks and has a worldwide distribution. Two important species in cattle—Babesia bigemina and Babesia bovis—are widespread in tropical and subtropical areas and are the focus of this discussion. In endemic areas, two features are important in determining the risk of clinical disease: 1) calves have a degree of immunity (related both to colostral-derived antibodies and to age) that persists for ˜6 months, and 2) animals that recover from Babesia infections are immune for life. Thus, at high levels of tick transmission, all newborn calves will become infected with Babesia by 6 mos. of age, show few if any clinical signs, and subsequently be immune. This situation of endemic stability can be upset by either a natural (eg, climatic) or artificial (eg, acaricide treatment) reduction in tick numbers to levels where tick transmission of Babesia to calves is insufficient to ensure all are infected during this critical early period. Other circumstances that can lead to clinical outbreaks include the introduction of susceptible cattle to endemic areas and the incursion of Babesia-infected ticks into previously tick-free areas. Strain variation in immunity has been demonstrated but is probably not of significance in the field. The acute disease generally runs a course of ˜1 week. The first sign is fever (frequently 41° C. or higher), which persists throughout, and is accompanied later by inappetence, increased respiratory rate, muscle tremors, anemia, jaundice, and loss of weight with hemoglobinemia and hemoglobinuria in the final stages. CNS involvement due to sludging of parasitized erythrocytes in brain capillaries occurs frequently with B. bovis infection. Either constipation or diarrhea may be present. Pregnant cows often abort. With virulent strains of B. bovis, a hypotensive shock syndrome, combined with generalized non-specific inflammation, coagulation disturbances, and erythrocytic stasis in capillaries, contribute to the pathogenesis. With most strains of B. bigemina, the pathogenic effects relate more directly to erythrocyte destruction. Animals that recover from the acute disease remain infected for a number of years with B. bovis and for a few months in the case of B. bigemina. No signs are apparent during this carrier state. Lesions include an enlarged and friable spleen; a swollen liver with an enlarged gallbladder containing thick granular bile; congested, dark-colored kidneys; and generalized anemia and jaundice. The urine is often, but not invariably, red. Other organs, including the brain and heart, may show congestion or petechial hemorrhages. The susceptibility of cattle breeds to Babesia infections varies; for example, Brahman cattle are more resistant to B. bovis infection than are British breeds.
What is needed in the art is an immunogenic composition effective for eliciting an immunological response against M. bovis and at least one further cattle relevant pathogen. What is further needed is an immunogenic composition effective for lessening the severity of or reducing the incidence of signs of microbiological infections of cattle, caused by M. bovis and one or more other cattle relevant pathogen(s). What is still further needed is a vaccine effective for reducing or eliminating the incidence of signs of microbiological infections of cattle caused by M. bovis and one or more cattle relevant pathogen(s). What is still further needed is a method of treatment and/or prophylaxis of infections of cattle caused by M. bovis and one or more further cattle relevant pathogen(s) comprising a co-administration of M. bovis antigen and an immunologically active component of one or more cattle relevant pathogen(s). The co-administration may occur by the administration of two or more immunogenic compositions, each comprising one or more of the cattle relevant antigens including the M. bovis antigen, or by administration of a fixed-dose immunogenic composition comprising all the cattle relevant antigens, including the M. bovis antigen.